This invention relates to a brake fluid pressure control apparatus in a vehicle brake system of the type in which an anti-lock control mechanism is connected to a hydraulic booster.
The structure of a brake fluid pressure control apparatus of this type is shown in U.S. Pat. No. 4,750,289, U.S. Pat. No. 4,802,713, Japanese Laid-Open Patent No. 59-137242, Japanese Laid-Open Patent No. 61-77553, etc.
The apparatuses disclosed in the above-mentioned publications have the following structure: the rear end of a hydraulic brake booster is connected to the front end of a push rod of a brake pedal, and a master cylinder is connected to the front end of this hydraulic brake booster. The fluid chamber of this master cylinder is connected through a hold valve consisting of a normally-open type electromagnetic valve to a wheel cylinder. The wheel cylinder is connected to a reservoir through a decay valve consisting of a normally-closed type electromagnetic valve. Thus, the master cylinder is arranged on the downstream side of the brake booster.
The problem with the above conventional brake fluid pressure control apparatus is that the hydraulic brake booster and the master cylinder are connected in series to each other, resulting in the entire length of the apparatus being excessively large. Further, since the above-described connection in series also involves an increase in weight, a special reinforcement must be provided on the wheel side before this brake fluid pressure control apparatus can be mounted, for example, on the fire wall of the vehicle.